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POWER MANAGEMENT Fig. 1: LTC3388-1/-3 typlical application schematic. perspective, this adds a further degree of complexity since they must now take into consideration how much energy must be stored in the secondary reservoir to compensate for the lack of an ambient energy source. Just how much they will require will depend on several factors. These will include the length of time the ambient energy source is absent, the duty cycle of the WSN (that is the frequency with which a data reading and transmission has to be made), the size and type of a secondary reservoir (capacitor, supercapacitor or battery). Is enough ambient energy available to act as both the primary energy source and have sufficient energy left over to charge up a secondary reservoir when it is not available for some specified period? Ambient energy sources include light, heat differentials, vibrating beams, transmitted RF signals, or just about any other source that can produce an electrical charge through a transducer. Table 1 illustrates the amount of energy that can be produced from different energy sources. A nanopower IC solution It is clear that WSNs have very low levels of energy available. This, in turn, means that the components used in the system must be able to deal with these low power levels. While this has already been attained with the transceivers and microcontrollers, on the power conversion side of the equation, there has been a void. However, Linear Technology introduced its LTC3388-1/-3 to specifically address this requirement. The LTC3388-1/-3 is a 20V input capable synchronous buck converter than can deliver up to 50mA of continuous output current from a 3mm x 3mm (or MSOP10-E) package – see figure 1. It operates from an input voltage range of 2.7V to 20V, making it ideal for a wide range of energy harvesting and battery-powered applications including “keep-alive” and industrial control power. The chip uses hysteretic synchronous rectification to optimize efficiency over a wide range of load currents. It can offer over 90% efficiency for loads ranging from 15uA to 50mA and only requires 400nA of quiescent current, enabling it to provide extended battery life. The combination of its 3x3mm DFN package (or MSOP-10) and only five external components offers a very simple and compact solution footprint for a wide array of low power applications. The LT3388-1/-3 incorporates an accurate undervoltage lock-out (ULVO) feature to disable the converter when the input voltage drops below 2.3V, reducing quiescent current to only 400nA. Once in regulation (at no load), the LTC3388-1/-3 enters a sleep mode to minimize quiescent current to only 720nA. The buck converter then turns on and off as needed to maintain output regulation. An additional standby mode disables switching while the output is in regulation for short duration loads, such as wireless modems, which require low ripple. Even though portable applications and energy harvesting systems have a broad range of power levels for their correct operation, from microwatts to greater than 1W, there are many power conversion ICs available for selection by the system designer. However, it is at the lower end of the power range, where nanoamps of currents need to be converted where the choice becomes limited. Rapid charge controller supports MediaTek fast charge protocol Dialog Semiconductor plc has unveiled the world’s first AC/ DC rapid charge controller compatible with MediaTek’s new Pump Express fast charge protocol which claims to enable rapid charging of mobile devices up to 45 percent faster than conventional chargers. Dialog’s iW1680 is a single-chip solution that reduces charge times in USB AC/DC wall chargers with no bill of materials (BOM) cost premium compared with slower conventional charging technologies. The iW1680 uses Dialogs built-in, intelligent rapid charge digital algorithm that communicates with MediaTek Pump Express-compatible phones and dynamically scales the output voltage of the wall charger to deliver the optimized level required by the phone at any given time. The overall system cost is lowered by eliminating the need for an input buck converter in the phone and reduces charge times by enabling more efficient power transfer to the phone battery. The iW1680 rapid charge AC/DC controller embeds digital analysis on the primary side of the isolated power supply within the charger, supporting voltage scaling without the need for any intelligence on the secondary side. Dialog Semiconductor www.dialog-semiconductor.com Battery management IC is first to comply to MIPI BIF Infineon Technologies has developed the ORIGA 3 Battery Management IC to protect smartphone and tablet computer users from unpleasant surprises. The device’s proprietary PrediGauge technology enables accurate fuel gauging. ORIGA 3’s PrediGauge technology accurately determines remaining battery capacity under the most adverse conditions. Within a few minutes of battery relaxation the IC predicts the future OCV and therefore the charging state within an average accuracy range of one percent. Additional functions of ORIGA 3 comprise precise temperature sensing as well as inputs for several sensors such as external temperature, strain gauge, and humidity. All information gathered by the IC is transferred to the host device (smartphone or tablet) using the MIPI BIF digital protocol. The hardware authentication feature of ORIGA 3 helps to identify unauthorized batteries. The ORIGA 3 authentication is based on an enhanced version of elliptic curve cryptography (ECC). The ORIGA Digital Certificate feature allows individual keys for each chip. It also enables secure field updates of the firmware. Infineon Technologies www.infineon.com 30 Electronic Engineering Times Europe March 2014 www.electronics-eetimes.com


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